So it has been very warm where I live locally (27-32 degrees celsius, I think thats in the 80-90 Faren range) and my fuel pump has been kind of reluctant to start at first. When I try to turn the car on I crank it for about three seconds (or ot starts instantly then sputters out almost instantly), then you can hear the pump fire on and the car starts. Shes running a little leaner than usual over 5500 RPM as well. I figure it's a relay issue or something, which was a problem my Integra Type R had. My only other 4G63 cars were a 97 and 98 Eclipse GST and GSX and I was running Walbro 255lph hardwired and never had any fuel issues in the heat. The car I'm having the issue with is a 96 Evo IV with a stock fuel pump and wiring (110lph I believe) with Evo 6 560cc injectors and ECU currently running on a stock tune till I figure this out. Just curious if anyone else has had any similar issues with their 4-9's so I have an idea where to start. I've worked on a few Evo's at the shop I work in so I know my way around the cars, so don't be shy. Thanks in advance!

 

Have you done fuel pressure tests? Checked powers and grounds? Checked amp draw of the pump? You get a pump prime with these cars? Are you running out of fuel at WOT?

 

Sorry I should have included that info. I don't believe there is a prime switch. All connections are sound. Amp draw is lower than it should be according to a thread on mlr. I run lean at WOT. Fuel pressure will be extremely low until the pump actually fires on. Haven't done any tests while driving. I'll check if I can log it via evoscan.

 

Fuel pressure is low till the pump kicks in and amp draw is lower than usual. If this doesn't prime, it sounds similar to the 4g93 gdi. The computer only grounds the relay coil in start/run. What's the amp on initial turn on?
It sounds like your pump is tired or you may have corrosion in the wiring. I could only speculate. This engine has a MAF? Unplug it and see if it works better.

 

So I ended up pulling out the pump to bench test it. It comes on after a few seconds of giving it power and cuts on and off sporadically. Definitely a dunzo pump. Not sure if I'm going to throw in a Walbro or a Deutschwerks yet. Traced through all the wiring too and replaced the relay cause why not. The engine does have a MAF. Evo's really didn't change much between 4-8 engine wise.

 

Cool, I hope the pump replacement solves your problem.